Among the weapons capable of attacking Iran's underground nuclear facilities, there is one that the US used early Sunday morning: the GBU-57A/B massive munitions penetrator (MOP), the largest non-nuclear "bunker-buster" bomb in the world, exclusively owned by Washington.

Senior officials from the Department of Defense confirmed the use of this precision-guided weapon, weighing 13,600 kg, something that the Pentagon also did on Sunday morning.

It was confirmed that this is the first time this bomb has been used.

US said Iran’s nuclear program had been “destroyed,” but Iranian television claimed the damage was not significant and the bases had been evacuated.

According to the U.S. government, the GBU-57A/B is a “large penetrating weapon capable of attacking deep, fortified bunkers and tunnels.”

At six meters in length, it is believed to be capable of penetrating approximately 61 meters below the surface before exploding. Multiple bombs can be dropped in succession, creating even more holes with each blast.

Manufactured by Boeing, the MOP has never been used in combat but has been tested at the White Sands Missile Range, a US military testing site in New Mexico.

It is more powerful than the Massive Ordnance Air Blast (MOAB), a 9,800kg weapon known as “the mother of all bombs,” which was used in combat in Afghanistan in 2017.

Limited arsenal

“The US Air Force worked hard to develop weapons very similar in size to the MOAB, but with the explosive charge contained within an extremely tough metal casing. The result was the GBU-57A/B Massive Ordnance Penetrator (MOP),” Paul Rogers, emeritus professor of Peace Studies at the University of Bradford (UK), explained a few days ago.

Currently,Only the American B-2 Spirit – also known as the stealth bomber – is configured and programmed to launch MOP.

The B-2, manufactured by Northrop Grumman, is one of the most advanced warplanes in the US Air Force arsenal.

According to its manufacturer, the B-2 can carry a payload of 18,000 kg.

However, the US Air Force says it has successfully tested the B-2 to carry two GBU-57A/Bs, giving it a total weight of about 27,000 kg.

The long-range heavy bomber has a range of about 11,000 kilometers without refueling, and up to 18,500 km with an aerial refuel, allowing it to reach almost anywhere in the world in a matter of hours, according to Northrop Grumman.

Rogers said that If MOP were ever used against an enemy with modern air defenses, such as Iran, the B-2 bombers would likely be joined by F-22 stealth attack aircraft to suppress the defenses, followed by drones to assess the damage and determine if further strikes are needed.

The expert estimated that the United States has a limited stockpile of these MOP bombs.

“They probably have an operational stockpile of about 10 or 20 of these bombs total,” he said.

Fordo

Fordo is Iran’s second nuclear enrichment facility after Natanz, its main one.

It is built into a mountainside near the city of Qom, about 95 km southwest of Tehran. It is believed to have begun construction around 2006 and to have become operational in 2009, the same year Tehran publicly acknowledged its existence.

In addition to being buried about 80 meters beneath rock and earth, Fordo is protected by Iranian and Russian surface-to-air missile systems.

In March 2023, the International Atomic Energy Agency (IAEA) detected particles of 83.7% enriched uranium, almost weapons-grade, at the site.

“Our objective was the destruction of Iran’s uranium enrichment capability and a halt to the nuclear threat posed by the world’s number one state sponsor of terror,” Trump said in a televised statement Saturday, after announcing the attack on Fordo and two other nuclear facilities, Natanz and Isfahan.

Iran has long maintained that its nuclear program is entirely peaceful and has never sought to develop a nuclear weapon.

But last week, the IAEA's 35-nation Board of Governors declared that Iran had breached its non-proliferation obligations for the first time in 20 years.

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